This invention relates in general to systems for programming implantable medical devices, and more particularly to programmers used to program the implantable devicesxe2x80x94programmers that use an audio locator signal to find the desired telemetry location for programming the implantable device.
Implantable medical devices are commonly used today to treat patients suffering from various ailments, including by way of example, pain, incontinence, movement disorders such as epilepsy, Parkinson""s disease, and spasticity. Additional implantable medical device therapies appear promising to treat a variety of other medical conditions, including physiological, psychological, and emotional conditions. As the number of implantable medical device therapies increases, so do the demands placed on these medical devices.
Known implantable medical devices, such as, cardiac pacemakers, tachyarrhythmia control devices, drug delivery devices, and nerve stimulators, provide treatment therapy to various portions of the body. While the present invention may be used with all implantable medical devices, by way of example and illustration, a drug delivery device will be discussed during the remainder of this section to illustrate the advantages of the invention. In the case of providing drugs to the patient, a drug delivery pump having a drug reservoir is implanted within the body. The pump is coupled to one or more catheters to deliver the drug from the reservoir to select portions of the body. The implantable drug pump provides steady, long-term delivery of drug therapy to the body and eliminates the need for frequent intravenous drug injections. Each implantable pump typically includes not only a refillable drug reservoir, but also a flow control device for regulating the drug delivery rate and, if needed, bolus injections.
Implantable drug pumps are well known in the art. Various forms of the drug pump are disclosed in U.S. Pat. Nos. 4,692,147 and 5,445,616, and are manufactured by Medtronic, Inc., Minneapolis, Minn., under the name Synchromed(copyright) drug infusion systems. The subject matter of these patents is incorporated herein by reference. Known drug delivery pumps may be either fixed rate pumps or programmable pumps. In the case of fixed-rate pumps, adjustment of the delivery rate and therefore the drug dosage may not be altered. In contrast, the drug delivery rate may be adjusted with a programmable pump through programming or reprogramming of the pump controller located within the pump. The physician may need to adjust the settings of the implanted pump for any number of reasons including, for example, to fine tune the therapy, to account for changes in the disease being treated, or to account for migration of the implanted catheter.
To achieve the programming or reprogramming of the implanted pump, a physician using an external controller, establishes a two-way telemetry communication link with the implanted pump. Once the communication link is established, through the use of radio frequency (RF) transmission, the physician may reprogram the modes of operation, parameters, and other functions of the implanted pump. In addition, the implanted pump communicates, via RF transmission, information stored in an internal memory regarding its operational status to the physician.
Specifically, a two-way telemetry link is established through the use of an RF transmitter and receiver located within the implanted pump. There is a corresponding RF transmitter and receiver in the external programmer or programming unit. Within the implanted pump, the transmitter and receiver use an antenna for receiving downlink telemetry signals and for radiating low amplitude RF signals for uplink telemetry. The telemetry transmission link used with known implanted medical pumps relies upon the generation of a low amplitude magnetic field by current oscillating in an LC circuit of an RF telemetry antenna in a transmission mode and the sensing of currents induced in a RF telemetry antenna in a receiving mode. The RF telemetry antenna of the implanted device is typically coiled wire wound around a ferrite core that is located within an airtight enclosure. The RF telemetry antenna of the programmer is contained in a programming head together with a permanent magnet which is placed over the patient""s skin and over the implanted device to establish a magnetic field with the implanted device. Today, both analog and digital data can be transmitted by uplink RF telemetry from the implanted pump to the programmer.
Presently, there is a trend toward providing some degree of patient control over the reprogramming of implantable medical devices. In the case of drug delivery systems, clinical studies show that actual drug usage may be reduced if a patient believes that he or she has some degree of control over drug dosage. A terminally-ill patient who has no ability to control or self-administer a drug will frequently insist on additional dosage at each visit to a physician as a precaution against exhaustion of the drug supply before the patient""s next office visit. In addition to these patient psychological aspects, there are added benefits of patient control. For example, in progressive diseases, the development of breakthrough pain may require an immediate increase in drug dosage. The ability to self-administer drug therapy may therefore reduce the number of office visits and provide immediate relief from breakthrough pain.
Before communication with, and reprogramming of, the implantable medical device can occur, the physician or patient must first locate the implantable device and then locate the desired telemetry position for programming. Presently, this is achieved by the programmer sending a wake-up pulse to the implantable device to wake up the device and begin polling the telemetry signal strength between the device and the programmer. For programming and/or monitoring of the implantable device, both uplink and downlink telemetry signal strength vary as a function programming head positioning relative to the implantable device. Therefore, it is important for the programming head to be properly positioned over the patient""s implant site so that downlink RF signals can be detected in the implantable device and uplink signals can be detected by the programming head of the external programmer. For example, if the programming head is too far away from the implantable device, the attenuation of RF signals transmitted across the boundary of the patient""s skin may be too great, preventing a telemetry link from being established.
Because positioning of the programmer is important for communication with the implantable device, appropriate feedback is required so that a user knows when a proper telemetry link has been established between the external programmer and the implanted device. The feedback also permits the user to position and reposition the programming head over the implant site until a suitable position is located.
In the past, various feedback techniques have been used to indicate to a user when a valid two-way telemetry link has been established. For example, programmers using a visible indicator, such as a light emitting diode (LED) or a visible alpha-numeric display, have been used to assist the physician or patient to find the desired telemetry location for the implanted device. Through variations of the visible indicator, a physician or patient will know the relative location of the programmer and the implanted device. When the programmer is in the proper telemetry position and the signal strength and accuracy are confirmed, the programmer control circuitry will cause the light indicator to indicate that a link has been established.
Programmers incorporating a visible indicator, however, suffer from many drawbacks. For instance, the visible indicator on these programmers is sometimes difficult to see depending on the orientation of the device. In addition, an implanted device is not always implanted in a location that lends itself to visual observation of the LED or visible indicator of the programmer, for example, when an implantable device is implanted in the patient""s back. The visual indicator may also be difficult to see for patients with poor vision or who suffer from physical limitations, for instance, patients who cannot bend over to observe the programmer when positioned over the abdomen.
Other known programmers have utilized tactile feedback to assist the user in locating the implanted device. The programmer will vibrate when the programmer is in the desired telemetry position. These programmers, however, are ineffective for patients with spastic conditions due to tremors in their hands. This is most common with implantable drug delivery systems which are used to treat spastic conditions. In addition, if the patient is in a bumpy environment, such as a car or bus, tactile feedback would also be ineffective.
It is therefore desirable to provide a programmer that overcomes the known disadvantages with the prior art and locates the desired telemetry location for an implantable medical device.
In an exemplary embodiment, the present invention provides for the use of audio feedback in conjunction with the positioning of the programmer for performing telemetry between the implantable device and the programmer. Audio feedback allows a user to locate an implantable device with a hand-held programmer without looking for an indicator light or alpha-numeric display, or without trying to sense a vibration in the programmer. In one embodiment, the programmer resonates audio tones that may vary in frequency depending on the relative position of the programmer and the implanted device. Once the desired telemetry location is located, the programmer notifies the patient to that effect through the use of another audio indicator.
The full range of objects, aspects and advantages of the invention will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.